The so-called attribute, which signifies properties and features that are inherent in things or matters, herein, is comprised of an attribute name and an attribute value. One thing or one matter has a plurality of the attributes. For example, when CPU of a certain personal computer are 1 GHz and a memory thereof is 500 MB, the number of the attributes of above personal computer is two, and one is attribute name CPU/attribute value 1 GHz, and the other is attribute name memory/attribute value 500 MB.